Coded railway signaling systems employing normally energized reversible track circuits



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3,075,075 CGDED RAILWAY SlGNALlNG SYSTEMS EM- PLOYING NORMALLY ENERGIZED RE- VERSIBLE TRACK CHiCUlTS Clifiord D. Earig, Penn Hills Township, Allegheny County,

Pa, assignor to Westinghouse Air Brake Company,

Wilmerding, Pa, a corporation of Pennsylvania Original application Sept. 7, 195a, Ser. No. 454,251, new

Patent No. 2,954,463, dated Sept. 27, 1960. Divided and this application Sept. 8, 1959, Ser. No. 838,601

4 Claims. (Cl. Z ta-39 My invention relates to coded railway signaling systems, and particularly to a coded railway signaling system employing normally energized, reversible track circuits and of t e type in which the movements of trafiic through a stretch of railway track are directed from a centralized point, to provide what is commonly known as a contralized tratfic control railway signaling system. My invention further relates to systems of the type described, in which a stretch of railway track is arranged in such manner that the track sections therein are normally energized with steady energy, this energy being changed to cod-ed energy of a suitable type and direction when a train movement is to be made through the stretch.

The present application is a division of my copending application tor Letters Patent of the United States Serial No. 454,251, filed September 7, 1954, for Coded Railway Signal Systems Employing Normally Energized, Reversible Track Circuits, now Patent No. 2,954,463, issued September 27, 1960.

In systems of this general type, as previously proposed, it has been customary practice to provide a single block indication light on the control machine to indicate when a stretch of single track is occupied. Although this single block indication light will provide information to the control operator as to whether or not a particular single track stretch is occupied by a train, it does not provide information as to the relative progress of the train, such as would be accomplished by providing at least two block indication lights. It would be of considerable assistance to the operator to have two block occupancy lights in each single track stretch, each light indicating when at least one half of the single track stretch is occupied. Further assistance to the operator may be obtained if the portions of the stretch covered by each light overlap, so that at times both lights simultaneously indicate track occupancy.

In systems of this general type, provision is made for the control of hand-operated switches located at some point in the single track stretch between passing sidings, such hand-throw switches being governed by electric switch lock-s, which require the cooperation of the train crew and the control operator before the hand-throw switch can be unlocked to permit a train to enter or leave a spur track at that point. In circuits heretofore used, in which the unlocking control for a move through a hand-throw switch equipped with an electric switch lock is obtained by measuring a time interval following the entrance of a train into a track section in which the electrically locked switch is located, it has been necessary to provide conventional track circuits to obtain the timing operation. Such conventional track circuits must be by-passed with line wires to carry coded track energy around the conventional track circuit to provide coded operation for the remainder of the track sections in the stretch.

Moreover, in systems of this general type as previously proposed, the control of such switch locks has been accomplished by a number of line wire circuits extending from a control location to the switch lock location, since it is necessary to provide suitable indications to the control operator of the conditions at the hand-throw switch location. It is of course desirable to keep the number'- of line wires necessary for these control circuits to a minimum. It is even more desirable to eliminate the line wires which pass the coded track circuits around the conventional track circuits at the switch location, since these wires are more vulnerable to the elements and are thus more likely to cause track circuit failures which result in unnecessary delays to through trains. It would be highly advantageous to carry as many as possible of the controls and indications for the switch lock in the track circuits used for the basic signal system, eliminating entirely the short conventional track circuits and the by-pass line wires and requiring only short wire leads from the nearest intermediate signal {or the majority of the controls and indications.

Accordingly, an object of my invention is to provide a railway signaling system of the centralized tratfic control type in which the'control of an electric switch lock located in a single track stretch is obtained "by-utilizing steady energy to check that the stretch is unoccupied by an opposing train and that no'conflicting controlled signal is clear before a switch can be unlocked for a move therethrough from a spur track. Thus, an unau-. thorized manipulation of the electric lock mechanism cannot disturb the signals for an established train move-,

ment.

An additional object of my invention is to provide, in a system of the type described, means for supplying an indication to the control operator to operate the system to change the steady energy normally supplied to the single track stretch to coded energy to provide suitable approach locking for protection of the hand-throw switch.

A further object of my invention is the provision of a switch locking control circuit, for entering moves into a siding, including a suitable time element means con trolled by coded track energy for timing the occupancy of the track section in which the switch lock is located.

It is also an object of my invention to provide an improved arrangement for governing the control and indication of the electric switch locks in a single track stretch used in a system of the type described, in which a minimum number of line wires is employed between the main control point and the switch lock location, the. circuits using a series type control to provide the necessary controls and indications so that two less wires are required over previous arrangements.

Still another object of my invention is the provision of a novel arrangement of circuits in the control machine for sending a suitable control code to a field location when an indication is received at thecontrol machine from the field location that the presence of steady energy at a switch lock location has been properly detected.

Other objects, purposes, and characteristic features of my invention will be apparent from the following description taken in connection with the accompanying drawings.

In practicing the invention, I first provide suitable circuits associated with the single track stretch for -checking the occupied or unoccupied condition of the track sections, which circuits are arranged to send suitable indications to the control ofiice for the control of two approach indication lamps on the control machine. The indication lamps are controlled in such manner that the lamps are normally dark. They are lighted over contacts of indication relays which are controlled by the circuits in the field, and also over contacts of block indication relays, so that the lamps are lighted only when a train is occupying the single track stretch and coded energy is being supplied thereto for the control of the signals. I further provide a-suitable circuit Patented Jan. 22, 1963 at .a switch lock control location for checking the presence of steady energy in a single track stretch when a movement is to be made from a spur track through the hand-throw switchcontrolled by an electric lock;v These circuits are inwhich; the switch lock lies in orderto permit atrain on the mainirack to unlock the hand-throw. switch for a move.

into the spurtrack.

Ifs'hall describe oneforrn: of coded railway signaling systemzemibodying my invention, and shall then point out the novel features thereoijn thepclaims,

In; the accompanyingdrawings, FIGS. 1a, lb, 1c, 1d, 1e, 1f, 1g, 1/1, 1k, 1m, and In, when placed together in the manner; shown; in..the:orientation diagram-illustrated by FIG; 3,,constitute a diagrammatic view showing one em.- bodimentiof my inventiomasnpplied ton stretch of'single track railway extending betweemthe ends of two passing sidings atteaoh end of the stretch.

FIGS. 2a, 2b, 2c, 2d,.2e, 2f,',and 2g, whentaken' to; gether innth'e manner. shown in the-orientation diagram illustrated by FlG. 4, illustrate the. diagrammatic-circuits forit-hexapparatus located at the control. ofiicefor the C011. t-rolrof the. wayside signalingsystem shown in FIGS. 1a through In.

- Similar: reference characters-refer to similar parts ot-the apparatus :imeach of the .severalzviews,

Referriiigifirstto FIGS; lathrough. 1n, the stretchlof track? between thepassingtsidingsis divided bymeans of the usuali-insulatedfrail joints into a number of track 5621 tions. Each of these track sections iscquipped'twith a track circuit for detecting the occupancy of the 'sectionby a train, Thesections .l-T'and '91 at the extreme endsof the'sihgle trackstretch form detector sections for provid ing themsualdetector locking: for preventing-the operason of *a power operated switch whenatrainis occupying the-section including the switch. These track circuitsare of the conventionaltype inwhicha track battery is connected' across the rails; atone end of the section and a track relay, such as relays .ITR and 9TR, is connected across the rails' at-the other end of the-section. The track sections 2T, 4T, and 6T areprovided with coded track circuits; as will be subsequently expl'ained in detail. The signals which; govern t-rafic' movements through the-single track" stretch are the entering signals ZRA and 'Z RB at the left-hand or west end or the stretch, the entering signals, ltlLA and IOLB at the right-hand or east endof the stretch, ,and}. in addition, the-intermediate signals 48, 5S, 6S,' and"7S.' Each of these waysidesignals maybe or any suitable type, and" are here shown; as color light signals having a green lamp G, a yellow lamp Y, and a red lamp R, which whenl-ighted indicated clear, caution, and stop, 7

respectively.

Each (tithe sections 2T, 4T, and GT is actually provided with'two track circuits, one'eastbound'and one westbound, each of whichincludes atone end a code fol-lowing track relay designated by the reference character TR with a suitable prefix, and a source ofjtrack circuit energy, conveniently show-nos a. battery, at/the other end. The track circuitscouldobviouslyybe of the alternating current type, and my invention. contemplates such track circuits, the direct current type being shown only for purposes of simplicity. The track circuit current is. coded under theinfiu enceo f trafilc conditions, or as initiated by the operator at the central control. oifice. Depending upon the direction of trafiic movement, only one or. the other track circuit is efi'ective: at any onetime, aswill be. subsequently made clear. The reference characters for control relays involved in an eastbound move include the prefix R for right-hand, and those for relays which control westbound moves include the prefix L for left-hand, in order to makethe circuits and disclosure more readily understandable.

In the interests of simplifying the disclosure, there is shown and described a system which employs but two code rates, these comp-rising direct current periodically inter-- rupted at the rate of 75 times per minute to provide a caution aspect on the signals and times per minute for providing a clear aspect on the signals. The coding of the energy which is supplied to the track circuits is controlled by means of suitable code transmitters, illustrated by conventional symbols and designated by the reference characters '7SCT and 189C? These units are constructed, in a mannerwcil known in the art, to operate their contacts recurrently at the rates of 75 and 180 times per minute when the operating windings of the code transmitters are supplied with energy. It is who understood that in the event cab signal apparatus on the trainsmoving through the stretch is to be controlled by the operation of the signaling system, alternating current energy coded over contacts controlled by these code transmitters may be superimposed upon the direct current trackv circuits, in a manner well known in the art. Following train movements maybe made throughout the stretchsince directional stick relays are provided-at the various intermediate locations, and afiter having once established traffic in a given direction, no further action on the part of the control operator other than the clearing of the entering signal to the stretch is required to permit entry ofa following train.

Itis to be understood that the office and'field stations, one suchfield. station "being located at each end of the single track stretch,;are connected over a pair of line wires, not shown, by a code communicationsystem which may be ofthe type shown in Letters Patent of the United States No. 2,229,249, issued January 21,1941, to Lloyd V; Lewis, for Remote-Control Systems, orin Letters Patent of the United States No. 2,411,375, issued November 19, 1946, to ArthurP. Jackal, for Remote Control Systems, or-as; described in detail in Manual 506A, published October 1950 by The Union Switch and Signal Company, andent-itledflime Code Control System.

Consideration of the detailed mode of operation of the code communication system is not needed for an understanding-of this invention and it is deemed sufiioient to point out that afield station is provided at each end of eachtrack stretch to be controlled. Coding units are providedat the ofiice and at eachfield station and are con nected bya pair of line Wir 5, Il0l shown, over which control; codes; are at times transmitted from the ofiice to a selected field station as a resultof the operation of suitable code starting-circuits in the control machine. At other times, indication codes are transmitted over the same linewires fromthc different field stations to the ofilce without interference. Each code includes a distinctive code call by means of which one station only is, selected to chest temporary establishment of communication channels between the office and station. Consequently the differentstations, for the diiferent panels on the office machine,- are not selected at the same time, and the same channel-s provide communication at different times with all of the stations. In order to simplify the explanation of the invention, the channels .are illustrated herein as sepa rate direct wire circuits extending between the office and field stations, as designated by similarly numbered terminals on the boxes indicated by the dotted lines as comprising the ofiice and field stations, with only those relays in volved in the code system shown which are necessary for an understanding of; theinvention.

The ofiice and the several wayside locations are each provided with a suitablesource ofdirect current energy, which may be a low voltage battery, of proper size and capacity. However, since the use of such sources is Well known, only the positive and negative terminals thereof are shown in the drawings, designated by the reference 

1. IN A CENTRALIZED TRAFFIC CONTROL SYSTEM FOR A STRETCH OF SINGLE TRACK RAILROAD INCLUDING A COMMUNICATION SYSTEM FOR TRANSMITTING CONTROL CODES FROM A CONTROL OFFICE TO FIELD STATIONS AT EACH END OF SAID STRETCH AND FOR TRANSMITTING INDICATION CODES FROM THE FIELD STATIONS TO THE OFFICE, SAID STRETCH BEING EQUIPPED WITH A REVERSIBLE TRACK CIRCUIT SYSTEM WHICH IS NORMALLY ENERGIZED WITH STEADY ENERGY FED FROM THE ESTABLISHED ENTRANCE END OF SAID STRETCH TO THE ESTABLISHED EXIT END OF SAID STRETCH, THE STEADY ENERGY BEING REPLACED BY CODED ENERGY SUPPLIED FROM THE ESTABLISHED EXIT END OF SAID STRETCH TO THE ESTABLISHED ENTRANCE END OF SAID STRETCH WHEN THE STRETCH IS CONDITIONED FOR A TRAFFIC MOVEMENT THERETHROUGH, A TRACK SWITCH LOCATED WITHIN SAID STRETCH, AN ELECTRIC SWITCH LOCK FOR GOVERNING THE OPERATION OF SAID SWITCH, MANUALLY ACTUATED MEANS ASSOCIATED WITH SAID SWITCH LOCK FOR REQUESTING A SWITCH UNLOCK, MEANS ASSOCIATED WITH SAID SWITCH LOCK FOR DETECTING THE PRESENCE OF STEADY ENERGY IN SAID TRACK CIRCUIT SYSTEM, MEANS GOVERNED BY SAID STEADY ENERGY DETECTION MEANS AND BY SAID MANUALLY ACTUATED MEANS FOR TRANSMITTING A SPECIFIC INDICATION CODE TO SAID CONTROL OFFICE ONLY WHEN THE STEADY TRACK ENERGY PERSISTS FOR A PRESELECTED TIME INTERVAL AND A SWITCH UNLOCK HAS BEEN REQUESTED, MEANS AT SAID CONTROL OFFICE RESPONSIVE TO SAID SPECIFIC INDICATION CODE FOR TRANSMITTING CONTROL CODES TO SAID FIELD STATIONS EFFECTIVE TO CAUSE CODED ENERGY TO BE SUPPLIED FROM BOTH ENDS OF SAID STRETCH TOWARD SAID SWITCH LOCK LOCATION, AND MEANS RESPONSIVE TO CODED TRACK ENERGY IS RECEIVED FROM BOTH ENDS OF SAID STRETCH FOR ANOTHER PRESELECTED TIME INTERVAL. 